with tuppence for paper and string...

this would be my McGyvered vortograph attachment... which i don't think cost more than $20 to make... picked up a second hand plain filter at the camera store for $5 and a package of 5 small square mirrors (I only used three of them) at the craft store (don't think it cost more than $6 or $7 but i really don't recall)... stick it together with duct tape... and voila!

A Northyscope as Domenico says. Brilliant ... I wonder if I can get anyone to make me one? I'll have no chance of doing it for myself! Thanks for the illustration and instruction manual. @domenicododaro